# Kangaroo Physics Question

Hi everyone,

I’m attempting to re-model an existing 4-6 person table designed by Foster+Partners called the Arc Table (Image attached) and expanding it to an 8-10 person table with the central legs inspired by the Musmeci Bridge.

I’m using Kangaroo physics to simulate the tensile membrane but I’m having some issue’s reproducing the form. I’m not sure if the membrane template I’m using is the correct way to go about modelling the table and I’m open to better suggestions.

I’ve attached the Rhino file which contains the 3D model of the original table available off their website, along with my own geometry.

Thanks

The Arc Table Help.gh (26.5 KB) The Arc Table Help.3dm (9.4 MB)

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For the original table, the mesh topology was diagonal to what you have in your image above, with a valence 6 vertex in the middle.
Have a look at this old thread:

Thanks Daniel, I’ll check it out!

Hi Daniel, I’ve been playing around with the algorithm created by Florian and I’ve read Brady Peters original post and he comments on how they achieved the raised height of the centre of the table by giving the structural nodes of the mesh negative gravity. I understand the concept but not sure how to execute this in GH, would you be able to help?

Hi Kieran,

Have a look at this:
arctable.gh (18.7 KB)

The VertexLoads component applies the negative gravity.

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Fantastic, thanks Daniel!

Hi again Daniel, I’m attempting to bridge two of the tables together and I was wondering if you had any advice on the best way to go about that?

I’ve attached some quick sketches of what I hope to achieve. Thanks, Kieran

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I’d first modify the base mesh something like this-
Take the hexagon composed of 6 quads from the start of the last definition I posted.
Copy paste it.
Subdivide one of them 2 times with WbSplitQuads, and the other just once.
Scale down the less subdivided one to approximately match the quad sizes.
Delete 4 faces from one, then move the control points of the other so they match up.
Then Join, AlignVertices and Weld to make it all one mesh.

Do the same for however many modules you want.
Then apply the same logic as before - subdivide it further, pull some points up and some down, and relax the mesh.

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Ahh ok, I attempted to do something similar but didn’t think to delete the quads. Thanks a lot!

This worked a treat but I’ve had to extend the legs to show the arch of the bridging section . Will I need to apply another Vertex load to the bridge to extend this arch? (as seen in my previous sketch) Cheers, Kieran

One way would be to separate the different sides of the boundary curve and assign them different tensions:

arctable_extend.gh (24.2 KB)

If you can’t get the shape you want this way you might find you need to adjust the anchor positions or the mesh topology.

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Thank for your help, Daniel. It looks great but I seem to be having issues with the bridge arch geometry. Also, when attempting to scale the bounding box beyond a certain threshold I lose all mesh thickness. I’ve tinkered with a few parameters but can’t seem to reduce the scale below about 0.740 and i’m not sure why? Thanks, Kieran

Arch Table Extend.gh (30.3 KB)

Actually it was a simple fix by adjusting the tension of bridge!

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I think this will do for now. There are still bits I’m not happy with but maybe that is for the future. I ended up adjusting the control points, as you said and raising the edge of the bridge and allowing for a wider arch. I also widened the bridge anchor points so they run (nearly) parallel with the hexagon sides and I think this worked well!

That was an interesting exercise, thank you for your help Daniel, I learned a lot!

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